1. Field
The present invention relates to an apparatus and a method of fabricating a liquid crystal display panel, and more particularly, to an apparatus and a method of fabricating a liquid crystal display panel for coating a photo-resist layer on a substrate.
2. Description of the Related Art
Recently, the importance of display devices has increased with an increase in the types of visual information transferring media available as well as the types and amount of information being transferred. Among the common devices, the cathode ray tube (CRT) is widely used. However, the CRT is heavy and large, neither of which is advantageous for use in portable electronic applications. Therefore, various types of flat display devices have been developed to overcome these defects.
The various types of flat display devices include a liquid crystal display (LCD) panel, a field emission display (FED), a plasma display panel (PDP) and an electro-luminescence (EL). These devices are available for sale in an assortment of forms.
Among these, the liquid crystal display panel can be used in electronic devices that are light, thin, and small. In addition, the mass productivity of liquid crystal display panel is continually being improved, so it has been rapidly replacing the CRT for many applications.
One type of liquid crystal display panel, using an active matrix, has excellent picture quality and low power consumption. The active matrix liquid crystal display panel is speedily being developed to larger size and high resolution using mass production technology and a result of research and development. The active matrix liquid crystal display panel drives liquid crystal cells by using thin film transistors (hereinafter “TFT”).
A liquid crystal display device, displaying a picture through the liquid crystal display panel, controls light transmittance of a liquid crystal material using an electric field to thereby display a picture. To this end, the liquid crystal display device includes a liquid crystal display panel having the liquid crystal cells arranged in an active matrix form, and driving circuits for driving the liquid crystal panel.
FIG. 1 is a perspective view illustrating a related art liquid crystal panel.
Referring to FIG. 1, the related art liquid crystal display panel 1 includes a color filter array substrate 20 and a TFT array substrate 30 that are combined each other with a liquid crystal layer 10 positioned therebetween. The liquid crystal display panel 1 shown in FIG. 1 represents a portion of a full effective display.
In the color filter array substrate 20, a color filter 24 and a common electrode 26 are formed on a rear surface of an upper glass substrate 22. A polarizer 28 is attached on an entire surface of the upper glass substrate 22. The color filter 24 includes the color filter layers of red R, green G and blue B colors that transmit light of particular wavelength bandwidth to display colors corresponding thereto, respectively. A black matrix (not shown) is formed between the color filters 24 adjacent with each other. The black matrix is formed between the color filters 24 of red R, green G and blue B to separate the color filters 24 of red R, green G and blue B from each other and to absorb the light incident from adjacent cells, to thereby prevent deterioration in the contrast of the device.
In the TFT array substrate 30, data lines 34 and gate lines 40 cross on an entire surface of a lower glass substrate 32. TFTs 38 are formed at the crossings of the data lines 34 and the gate lines 40, respectively. A pixel electrode 36 is formed at a cell region between each of the data lines 34 and each of the gate lines 40 in the entire surface of the lower glass substrate 32.
Each TFT 38 includes a gate electrode connected to a gate line 40, a source electrode connected to a data line 34 and a drain electrode facing the source electrode with a channel positioned therebetween. The TFT 38 is connected to the pixel electrode 36 via a contact hole passing through the drain electrode. The TFT 38 selectively provides a data signal from the data line 34 to the pixel electrode 36 in response to a gate signal from the gate line 40. The TFT 38 switches a data transferring path between the data line 34 and the pixel electrode 36 in response to the gate signal from the gate line 40, to thereby drive the pixel electrode 36. A polarizer 42 is disposed on a rear surface of the TFT array substrate 30.
The pixel electrode 36 is positioned in a cell region partitioned by the data line 34 and the gate line 40 and is made of a transparent conductive material having a high light transmittance. The pixel electrode 36 generates a potential difference along with a common electrode 26, which is formed on the upper glass substrate 22, by a data signal inputted via the drain electrode. The liquid crystal layer 10 adjusts an amount of light transmitted therethrough via the TFT array substrate 30 in response to an electric filed applied thereto. The liquid crystal material of the liquid crystal layer 10 positioned between the lower glass substrate 32 and the upper glass substrate 22 rotates due to a dielectric anisotropy by the potential difference between the pixel electrode 36 and the common electrode 26. Accordingly, the light from a light source is transmitted toward the upper glass substrate 22.
Polarizers 28 and 42 disposed on the color filter array substrate 20 and the TFT array substrate 30 transmit the light polarized in any direction. When the liquid crystal material of the liquid crystal layer 10 is 90° twisted nematic (TN) mode material, the polarization directions of the polarizers 28 and 42 are perpendicular to each other. An alignment film (not shown) is formed on the facing surfaces of the color filter array substrate 20 and the TFT array substrate 30.
In order to form a pattern on the color filter array substrate 20 or the TFT array substrate 30, a photo-resist is applied to the upper glass substrate 22 or the lower glass substrate 32 including a thin film having a conductive layer, an insulating layer or a semiconductor layer. Thereafter, an exposure process selectively irradiating the photo-resist with ultraviolet rays using a photo mask and a development process developing the exposed photo-resist are performed to form a photo-resist pattern. The photo mask includes a mask substrate made of a transparent substance whose exposed area becomes an exposure area, and a shielding layer formed on the mask substrate to make a shielding region. The thin film is patterned through an etching process using the photo-resist pattern as a mask, to thereby provide the pattern.
FIG. 2 is a perspective view illustrating an apparatus for coating a photo-resist layer on the substrate, and FIG. 3 is a sectional view illustrating the operation of the coating apparatus shown in FIG. 2.
The coating apparatus shown in FIGS. 2 and 3 includes a stage 50 on which an upper or a lower glass substrate 22 or 32 is mounted, and a slit nozzle 52 for applying a photo-resist liquid 54 on the upper or the lower glass substrate 22 or 32.
The slit nozzle 52 is separated from the upper or the lower glass substrate 22 or 32 by a distance of 30 μm to 200 μm and is moved along a longitudinal direction of the upper or the lower glass substrate 22 or 32, so that it applies the photo-resist liquid 54 on the upper or the lower glass substrate 22 or 32 to form a photo-resist layer 56.
Even though the slit nozzle 52 is separated from the upper or the lower glass substrate 22 or 32 by the distance of 30 μm to 200 μm to apply the photo-resist liquid 54 to the upper or the lower glass substrate 22 or 32, bubbles occur upon forming the photo-resist layer 56 on the upper or the lower substrate 22 or 32, as shown in FIG. 3. In this case, a poor photo-resist layer is formed when the photo-resist layer 56 is further processed, such as when it is baked at a temperature of 100° C.
Further, if the photo-resist layer 56 is coated on an upper or lower glass substrate 22 or 32 that has impurities, then the slit nozzle 52 applying the photo-resist liquid on the upper or the lower glass substrate 22 or 32 may be damaged. In addition, the upper or the lower glass substrate 22 or 32 may also be damaged.